Abstract factory pattern

• Abstract Factory patterns work around a super-factory which creates other factories. This factory is also called as factory of factories. This type of design pattern comes under creational pattern as this pattern provides one of the best ways to create an object.
• In Abstract Factory pattern an interface is responsible for creating a factory of related objects without explicitly specifying their classes. Each generated factory can give the objects as per the Factory pattern.
• We are going to create a Shape and Color interfaces and concrete classes implementing these interfaces. We create an abstract factory class AbstractFactory as next step. Factory classes ShapeFactory and ColorFactory are defined where each factory extends AbstractFactory. A factory creator/generator class FactoryProducer is created.
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• Step 1
public interface Shape { void draw(); }
• Step 2
public class Rectangle implements Shape { @Override public void draw() { System.out.println("Inside Rectangle::draw() method."); } }
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public class Square implements Shape { @Override public void draw() { System.out.println("Inside Square::draw() method."); } }
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public class Circle implements Shape { @Override public void draw() { System.out.println("Inside Circle::draw() method."); } }
• Step 3
public interface Color { void fill(); }
• Step 4
public class Red implements Color { @Override public void fill() { System.out.println("Inside Red::fill() method."); } }
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public class Blue implements Color { @Override public void fill() { System.out.println("Inside Blue::fill() method."); } }
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public class Green implements Color { @Override public void fill() { System.out.println("Inside Green::fill() method."); } }
• Step 5
public abstract class AbstractFactory { abstract Color getColor(String color); abstract Shape getShape(String shape) ; }
• Step 6
public class ShapeFactory extends AbstractFactory { @Override public Shape getShape(String shapeType){ if(shapeType == null){ return null; } if(shapeType.equalsIgnoreCase("CIRCLE")){ return new Circle(); }else if(shapeType.equalsIgnoreCase("RECTANGLE")){ return new Rectangle(); }else if(shapeType.equalsIgnoreCase("SQUARE")){ return new Square(); } return null; } @Override Color getColor(String color) { return null; } }
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public class ColorFactory extends AbstractFactory { @Override public Shape getShape(String shapeType){ return null; } @Override Color getColor(String color) { if(color == null){ return null; } if(color.equalsIgnoreCase("RED")){ return new Red(); }else if(color.equalsIgnoreCase("GREEN")){ return new Green(); }else if(color.equalsIgnoreCase("BLUE")){ return new Blue(); } return null; } }
• Step 7
public class FactoryProducer { public static AbstractFactory getFactory(String choice){ if(choice.equalsIgnoreCase("SHAPE")){ return new ShapeFactory(); }else if(choice.equalsIgnoreCase("COLOR")){ return new ColorFactory(); } return null; } }
• Step 8
public class AbstractFactoryPatternDemo { public static void main(String[] args) { //get shape factory AbstractFactory shapeFactory = FactoryProducer.getFactory("SHAPE"); //get an object of Shape Circle Shape shape1 = shapeFactory.getShape("CIRCLE"); //call draw method of Shape Circle shape1.draw(); //get an object of Shape Rectangle Shape shape2 = shapeFactory.getShape("RECTANGLE"); //call draw method of Shape Rectangle shape2.draw(); //get an object of Shape Square Shape shape3 = shapeFactory.getShape("SQUARE"); //call draw method of Shape Square shape3.draw(); //get color factory AbstractFactory colorFactory = FactoryProducer.getFactory("COLOR"); //get an object of Color Red Color color1 = colorFactory.getColor("RED"); //call fill method of Red color1.fill(); //get an object of Color Green Color color2 = colorFactory.getColor("Green"); //call fill method of Green color2.fill(); //get an object of Color Blue Color color3 = colorFactory.getColor("BLUE"); //call fill method of Color Blue color3.fill(); } }
• Step 2